You can compare the features here:
Editions
I couldn't decide which version to get, I ended up with Fruity (glad I did, because FL Studio annoys me a lot and I prefer Studio One, FL Studio seems better for stuff that relies heavily of beats/drums to be used with its Patterns feature). The main difference between each version is the amount of extra sound packs you are buying (instead of buying them separately later), such as drum or synth sounds.
They have had a Black Friday sale in the past, so that would be a good time to upgrade from Fruity to a fancier version, or just buy additional sounds. But you could also just get extra sounds by adding free vsts to your library instead of purchasing the FL Studio ones.